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Greenland 5 km DEM, Ice Thickness, and Bedrock Elevation Grids

Entry ID

NSIDC-0092

Summary

A Digital Elevation Model (DEM), ice thickness grid, and bedrock elevation grid of Greenland acquired as part of the PARCA program are available in ASCII text format at a 5 km grid spacing in a polar stereographic projection. DEM data are a combination of ERS-1 and Geosat satellite radar altimetry data, Airborne Topographic Mapper (ATM) data, and photogrammetric digital height data. Ice thickness data are based on approximately 700,000 data points collected in the 1990s from a University of Kansas airborne ice penetrating radar (IPR). Nearly 30,000 data points were collected in the 1970s from a Technical University of Denmark (TUD) airborne echo sounder. Bamber subtracted the ice thickness grid from the DEM to produce a grid of bedrock elevation values. Applications include studies of gravitational driving stress and ice volume (mass balance) of the Greenland Ice Sheet. Each of the three grids is approximately 1.5 MB. Data are available via FTP. Data access is unrestricted, but we recommend that users register with us. Registered users automatically receive e-mail notification of product updates and changes to processing.

Instrument

Project

Quality

Various methods were applied to improve the accuracy of elevation estimates over the Greenland ice sheet, including waveform tracking, slope correction, data filtering (tests for return-echo waveform shape, backscatter coefficient, and retracking correction values for each altimeter height estimate), and removal of anomalous orbits.

Errors in the estimate of derived ice thickness measurements were determined by comparing the radar-based measurements with those from the Greenland Ice Sheet Project (GISP) and Greenland Ice Core Project (GRIP) ice cores. Results showed that radar-based measurements were within 10 m of ice core measurements. No corrections were made for firn effect.

Since elevation and ice thickness data from the 1970s were much less accurate than the 1990s data, errors in the merged grid were most significant where 1970s and 1990s tracks were in close proximity. Errors in the 1970s data did not cause anomalously high ice thickness gradients at a distance of three grid points (15 km) away from the 1990s data, so gridded data points closer than three grid cells to the 1990s data were removed (Bamber, Layberry, and Gogenini 2000). See guide document for a more complete description.